In general, washing of a drum washer is performed by friction between a drum and laundry rotated by a rotary force of a motor in a state that a detergent, wash water and laundry are thrown in the drum. The washing method has an effect of generating less damage to laundry, untangling laundry, and washing by rubbing.
Demand of a combination dryer and washer is increasing, the combination dryer and washer for performing not only washing and dehydrating, but also drying laundry.
The combination dryer and drum washer forcibly draws and heats outside air from a fan and a heater provided at outside of a tub, so as to dry laundry by blowing the heated air at a high temperature into the tub.
A drum type dryer attracts attention, not as a combination washer and dryer, enabling to dry a large amount of clothes for a short period of time at one time by performing drying only.
Hereinafter, an automatic drying apparatus applied to a combination automatic dryer and drum washer of related art is described as follows. FIG. 1 illustrates an example of a location of a temperature sensor used for determining dryness at the automatic dryer and drum washer.
Generally, a drum washer of related art employed a manual dry system, wherein a user selects a drying mode for setting a proper drying time according to a load of laundry.
However, the manual dry system does not meet the users satisfaction because drying operation is not exactly performed such that laundry is less or over dried.
For solving the problem, as illustrated in FIG. 1, a drying method is developed, performing drying operation by detecting a temperature in a tub 11 and a duct 12 by means of a tub temperature sensor (Ttub) provided in the tub 11 for detecting temperature of the inside of the tub, and a duct temperature sensor (TA1) provided in the duct 12 for detecting the temperature of the duct 12, and determining dryness according to a difference (T) of the detected Ttub and TA1.
FIG. 2 illustrates a graph showing a temperature change of the duct temperature sensor and the tub temperature sensor according to the drying operation, and FIG. 3 illustrates a graph showing a change of difference between the duct temperature sensor and the tub temperature sensor.
In a condensing dry method, laundry is dried by repeating a process of drawing high temperature and low humidity air into the tub, and passing the high temperature and low humidity air through the duct such that the air drawn into the tub absorbs humidity from laundry and changes into high temperature and high humidity air by the condensing process.
In this case, the air changed into low temperature and low humidity air by the condensing process is changed into high temperature and low humidity air by a heater and is drawn back into the tub.
In the drying process, the temperature change of the tub temperature sensor (Ttub) and the duct temperature sensor (TA1) is as follows.
First, as illustrated in FIG. 2, in a first stage of drying process, since laundry in the tub contains a large amount of humidity, there is few temperature difference detected by the tub temperature sensor (Ttub) and the duct temperature sensor (TA1) because low temperature and low humidity air passes through the duct and a small amount of coolant and condensed water are collected on a lower end of the duct at a low temperature.
In a middle stage of drying process, high temperature air heated by the heater is continuously drawn for removing-humidity contained in laundry, and the temperature of the tub is continuously increased. Since the high temperature and high humidity air passes through the duct and is actively condensed, the temperatures detected by the tub temperature sensor (Ttub) and the duct temperature sensor (TA1) gradually increase by the same amount.
In a terminal stage of drying process, since the humidity contained in laundry is mostly removed and the high temperature and low humidity air passes through the duct, the temperature detected by the duct temperature sensor (TA1) is increased. In this state, since dryness of the laundry is high, the temperature detected by the tub temperature sensor (Ttub) is gradually decreased because the amount of condensed water is decreased and that of the coolant is increased.
Drying operation is divided into levels of Damp dry, Dry, and Strong dry by using the temperature difference value (ΔT) as a dryness determination value Δ. According to the level, drying is performed.
However, as abovementioned, the drying method of using the difference between the temperature in the tub and the temperature in the duct has problems as follows. The related art indirectly checks humidity in the washing tub by using the temperature sensor for performing an automatic drying algorithm. In other words, an estimated humidity is calculated by the temperature detection value by the temperature sensor in the duct or the tub. In other words, during the drying process, a degree of dryness is determined by calculating an average of data detected by the temperature sensor in a particular section. Accordingly, stability of data is lowered because a rotation period of a main motor rotating in first and second directions for driving the drum, a water supply period, and a drainage period are different from each other, and the periods are not consistent with a period of calculating the average value of the data.
It is noticed that the rotation period of the motor rotating in first and second directions and a point, when the temperature data is shaken, are consistent as shown in FIG. 4b illustrating an exploded view of (A) section of FIG. 4a showing temperature difference value of the duct temperature sensor and the tub temperature sensor in accordance with the drying operation.
FIG. 4b illustrates a graph showing a relationship between a motor period (CW_CCW) and temperature data. Waving of the temperature data makes it difficult to determine dryness exactly, thereby lowering reliability of automatic drying.
Since the method of drying by using the temperature difference between the temperature in the tub and the temperature in the duct uses a fixed dryness determination value, a passage structure is changed and it is difficult to perform drying exactly due to a location of the temperature sensor in the tub, deviation in the temperature sensor itself, deviation of the duct structure, and deviation of the heater performance.
Particularly, as illustrated in FIG. 5, when the fixed dryness determination value is used, it is difficult to perform the drying operation exactly because dryness is not determined consistently for all weights.
FIG. 5 illustrates a graph showing a change of the dryness determination value (A) at a point of achieving desired dryness according to weight.
For example, during drying operation for achieving 90% of dryness, if drying operation is performed when the dryness fixed value is set at ‘50’, the dryness value (Δ) at the point of achieving 90% of dryness differs according to the weight.
In other words, if the dryness determination value (Δ) is ‘25’ when the weight is 1 kg, it becomes ‘40’ for 2 kg, and ‘55’ for 4 kg, thus the automatic dryness detection is not exactly carried out.
In this case, the dryness determination value (Δ) is ADC decimal data, and does not have a range of dryness satisfying the demand of the user when the automatic dryness detection is not exactly carried out.
FIG. 6 illustrates a graph showing a range of dryness according to weights at each drying mode when the fixed dryness determination value (Δ) is used.
In FIG. 6, it indicates that drying is performed exactly when there are points represented as 1, 2, and 3 (1→1.0 kg, 2→2.0 kg, 3→4.5 kg) that are divided according to the weight in a block (a part indicated by a straight perpendicular line) at each corresponding drying mode respectively. However, when the points are displayed outside of the block, it indicates that drying is not exactly performed.
It is dryness having a level of y axis for a corresponding point, showing that the fixed dryness detection value (Δ) is detected at each point of 1, 2, and 3.
As illustrated in FIG. 6, in case of a small amount of laundry, desired dryness is achieved in each drying course, that is Dry, Strong, Damp, and LTD (Low Temperature Dry) when the drying operation is performed by using the fixed dryness determination value (Δ). However, dryness is lower with a larger amount of laundry.